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When Evolved Behaviors Backfire

Frogs that eat holiday lights, birds that eat plastic, and beetles attempting to mate with beer bottles are all examples of organisms that have fallen victim to what biologists call “evolutionary traps.” Whereas natural selection typically produces organisms that behave in ways to maximize their fitness, resulting in more offspring passing their genes onto the next generation, human actions sometimes short-circuit the process, causing behaviors shaped by natural selection to compromise an organism’s fitness or kill it outright. A recent paper by Bruce Robertson and colleagues reviews what we know about the causes and consequences of such traps, as well as potential solutions.

Mayflies are an illustrative case study cited by the author. Mayflies normally lay their eggs in natural water bodies which they find by keying in on the polarized light reflected by water. However, man-made structures like glass windows on storefronts also reflect polarized light, potentially attracting mayflies as a result. If the mayflies lay their eggs on a window, their reproductive efforts will fail and their energy will be wasted.

The authors identify potential solutions for evolutionary traps, such as limiting organisms’ access to habitats containing many man-made objects, limiting species’ exposure to traps during key moments in their life cycles, such as breeding, and redesigning structures and materials so they do not attract certain species as strongly. A good example of the last method in action comes from sea turtles: when they hatch from their beach nests, sea turtle hatchlings find their way to the ocean in part by moonlight reflected from the water at night. However, in many parts of the world beachfront residential areas are also sources of light during the nighttime, and hatchling sea turtles can end up going the wrong way. To remedy this problem, many beachfront communities regulate the amount of light they emit during hatching season. But unfortunately, with the ever-expanding human footprint on the planet, it seems likely that more species will fall into evolutionary traps more frequently in the future as they encounter more landscapes that have been fundamentally altered by human activity.